Recently, with increasingly stringent environmental regulations and to reduce energy costs, demand for eco-friendly electric vehicles (EVs) has increased. In the United States and Europe, electric vehicles will be forced into widespread use due to the Clean Air Conservation Act. Domestically, research into green cars has been actively conducted as a part of green growth.
A battery is provided in an electric vehicle in order to drive a motor for driving the vehicle and various electronic apparatuses. In addition, an air conditioner for air conditioning or heating is provided.
In addition, an integrated starter generator (ISG) for starting an engine and rotating a motor is provided in an electric vehicle. The ISG operates in a motoring mode for rotating the motor and a generating mode for generating a predetermined output voltage to charge a battery.
A plurality of batteries having different charging voltages may be provided in the electric vehicle. At this time, each battery may be charged in the generating mode of the ISG.
As the ISG is generally configured to generate a high output voltage, a high-voltage battery may be charged via the output voltage of the ISG but a low-voltage battery may not be charged via the output voltage of the ISG. Thus, a separate DC-DC converter is required.
That is, the DC-DC converter performs a function for decreasing the high output voltage of the ISG to a charging voltage of the low-voltage battery.
However, the DC-DC converter has a heavy weight and a large volume, thereby increasing the weight of the electric vehicle and reducing an internal space for use. In addition, the DC-DC converter may deteriorate efficiency of the electric vehicle.
Accordingly, even when a plurality of batteries having different charging voltages is provided, there is a need for a structure for charging each battery via a single ISG without a separate DC-DC converter.
In order to charge a high-voltage battery and a low-voltage battery using an ISG, rotation force of an engine should be delivered to the ISG. At this time, it is difficult to charge the high-voltage battery and the low-voltage battery using the ISG in a state in which the engine is not driven.
Accordingly, there is a need for a structure for emergency-charging a low-voltage battery even in a state in which an engine is not driven.